So I've implemented paypal IPN in my site and I'm in the middle of the work process. Now I want to use more than 1 custom variable in the pp form currently I'm using this one only
<input type="hidden" name="custom" value="<?php echo $user_id; ?>">
So I know the variable with the name 'custom' is allowed. I want to know if I can pass more variables so I can filter the payments based on their criterias. So if for example shipping is more than $0.00 I set a variable "shipping_cost" like this:
<input type="hidden" name="shipping_cost" value="<?php echo $cost; ?>">
or for other purposes. Is this allowed? Or paypal has an already defined list of allowed variables we can use? I really want to solve this problem as there's not always one type of payment we can process... Thank you guys.